Optical recording means are well known as shown in the following documents:
______________________________________ U.S. Pat. No. Issue Date Inventor(s) ______________________________________ 4,074,085 2/14/78 Russell 4,094,010 6/6/78 Pepperl et al 4,106,058 8/8/78 Romeas et al 4,138,663 2/6/79 Lehureau et al 4,315,283 2/9/82 Kinjo et al 4,375,091 2/22/83 Dakin et al 4,416,002 11/15/83 Oguino et al 4,443,870 4/17/84 Hazel et al 4,445,144 4/24/84 Giddings 4,449,212 5/15/84 Reno 4,453,239 6/5/84 Musha et al 4,462,095 7/24/84 Chen ______________________________________
In some prior art systems, such as shown in U.S. Pat. Nos. 4,106,058, 4,138,663 and 4,375,091 the optical recording disc is preformed with either concentric grooves or a spiral groove, within which grooves a data track is written. Formatting of grooved discs is not possible using the same machine that does the optical writing and reading of discs. In other prior art systems, such as shown in U.S. Pat. Nos. 4,106,058, 4,138,663, 4,416,002 and 4,445,144, no separate reference and data tracks are employed. With such arrangements, the probability of acquiring and/or jumping to a wrong track is large unless data tracks are relatively widely spaced. In prior art systems which include separate reference and data tracks, such as shown in U.S. Pat. Nos. 4,094,010, 4,315,283 and 4,443,870, only intermittent scanning of the reference tracks is employed. Even if continuous reference tracks are included, they are intermittently scanned in the above-mentioned systems. Without continuous scanning and tracking, highly accurate tracking is not possible. If every data track is provided with its own unique reference track, such as shown in U.S. Pat. No. 4,453,239, then the amount of data that can be sorted on the recording media is greatly limited.